A matrixed surround-sound system which combines multichannel LCRS audio in such a way that the encoded signal forms a stereo-compatible, two-channel format for recording and broadcasting. Originally developed in 1977 for “Star Wars,” and now in wide use. As with any matrix system, it is impossible to completely recover the original multichannel signals with perfect isolation. The decoder disguises this problem through a steering process which emphasizes the signal emanating from its appropriate loudspeaker by canceling out a portion of the crosstalk in adjacent channels. See also free encoding, Pro Logic.